Crafting Sustainable Rum is Largely a Matter of Catch and Release


After a few Mojitos, it's easy to forget that making rum is an industrial process. Photo credit: Distillery Serrallés, USA

In the first part of this series on rum production, we took a look at the environmental impacts and industry pitfalls inherent in traditional distillation. To make a long story short: The manufacture of one of the world's favorite spirits has been everything but clean and responsible.

Fortunately, some producers have begun to address these issues and the innovative systems they have implemented demonstrate that rum can make people feel good while doing some good, too.Recently, TreeHugger had the opportunity to take a look at the art and science—as well as the clean and dirty—of making rum first-hand, thanks to a trip sponsored by Distillery Serrallés for members of the press.

Though the basic practice of making rum—or producing alcohol from sugar—is thousands of years old, several distillers—including Distillery Serrallés—are finding that major improvements can be made simply by addressing the impacts of each step of the production chain.

And, as mentioned previously, that chain begins with growing sugar.

Taking the Bull By the Horns

Photo credit: hookbrother/Creative Commons

Growing and processing sugar is the first step of making rum—and it's also one of the most environmentally destructive—resulting in soil degradation and erosion, the overuse and pollution of local water resources, the spread of pesticides and fertilizers, emissions of greenhouse gases, and habitat destruction.

These impacts can be minimized, however, through the use of sustainable growing practices.

One notable advance has been the development of the Bonsucro Better Sugar Initiative which was originally designed to reduce the impacts of India and Brazil's burgeoning sugar cane biofuel industries. The standard—which has been ported to sugar-producing operations as well—governs fertilizer inputs, pesticide use, emissions, crop densities, and the treatment of human labor among other things and offers a plan sugar producers can follow to reduce the impact of their operations.

When it comes to rum, however, participation is limited by the economics of the industry. Sugar is more valuable as a fuel or sweetener than it is as high-quality molasses (which, remember, is really a byproduct of the refining process). This means that rum producers are often forced to pay sugar plantations to limit refinement—in addition to the cost of the molasseses—just to acquire a high-quality base.

There is something distilleries can do to counter this: Grow their own sugar cane. Slowly, this practice is returning to the industry. Producers like Verala Hermanos not only grow their own sugar cane, but have begun to implement some of the standards included in Bonsucro including employing local labor, harvesting by hand to reduce fuel consumption, and skipping the pre-harvest burn to reduce emissions.

Though there are obvious issues of scale with this approach, it is realistically the only way distillers can acquire sustainably-produced sugar in a economy that places more value on it when used in other applications.

Catching the Byproducts of Fermentation and Distillation

It's once the distiller has the molasseses that the real rum-making begins. At this stage, the most significant impacts come from energy expenditure and emissions. During fermentation, for example, the yeast emits larges amounts of CO2. What Distillery Serrallés and other producers have done to address this is to capture the CO2 and store it. Once captured, there is no fancy carbon sequestration done. Instead, it is simply sold to local soda manufacturers, who use it to carbonate their beverages.

It is during distillation—when steam is forced through columns to pull the alcohol from the fermented "rum beer"—that most of the energy is consumed. It is also during fermentation when the highly concentrated sludge—called mosto—is created. Dealing with the mosto is a complex process but the first stage—breaking down the remaining organic compounds with anaerobic bacteria—is relevant in that it produces volatile compounds. At Distillery Serrallés, these compounds are captured and concentrated into biogas, which is then used to offset 50 to 70 percent of the distillery's annual energy usage. The excess steam is used to power the distillation process.

Releasing What's Left

Crafting rum that's as clean as it looks is no easy task. Photo credit: Distillery Serrallés, USA

The anaerobic bacteria takes care of about 70 percent of the organic matter in the mosto. What remains, however, is far from clean.

What happens next is a unique process in the industry that was developed by Roberto Serrallés who, in addition to being a sixth generation rum maker also holds a PhD in Environmental Sciences from the University of Oregon.

To deal with remaining byproducts, Distillery Serrallés, separates any remaining solids from the liquid wastewater.

The liquids pass on to an open system that circulates and aerates the water. By bombarding the organic material with oxygen, it allows it to be rapidly digested by more bacteria. After this process, the organic content drops from about 1,000 to less than 150 parts per million. The wastewater is then passed through reverse osmosis membranes that further remove organics, dropping the count to nearly zero. The result is irrigation and industrial grade water that is then used to cool distillation equipment and water the grounds.

The solids that are separated from the wastewater follow a different path. They are combined with wood chips—made from broken shipping pallets and retired aging barrels—and made into compost. After some time in on-sight wind rows, the compost is sold to local landscapers, farmers, and gardeners.

Compared to the traditional process—which begins with industrial sugar cane and ends with a polluting sludge being dumped in a landfill or the ocean—these improvements to the rum making process are significant.

Of course, there are still opportunities for improvement, as we will see in the next and final installment of this series.

Read more about green liquor:
The Story of Sustainable Rum Begins With What's Left Behind
How to Go Green: Cocktails
Should You Shop For Organic Spirits?
Four Brands of Organic Booze To Get Your Party Started

Tags: Drinks | longreads | Pollution